 Spontaneous magnetization

Spontaneous magnetization is the magnetization that remains after taking the thermodynamic limit and then sending a symmetry-breaking external field to zero.

Spontaneous magnetization refers to the phenomenon where a material exhibits a net magnetization in the absence of an external magnetic field. This typically occurs in ferromagnetic or ferrimagnetic materials at low temperatures, specifically below their Curie temperature. In these materials, individual atomic magnetic moments (due to unpaired electron spins) tend to align in a uniform direction even without an external magnetic field.